If you have two bikes, one can test the other, Just jack the motor into the other bike if they use the common 9 pin motor plug, All you will need is the motor/wheel. If you get concerned about a controller failure, I suppose you can carry one, Honestly, with 10000 miles on a dozen bikes, I am trying to recall a component failure. I swap a lot of things but I can't recall anything that failed. Nothing, but I've broken four or five LCD displays with bikes falling over or flipping them upside down. That's like $160 in displays for carelessness.
What has failed? Freewheel wore out. Thumb shifter got too hard to push. Adjusters on brake levers fell apart. Pedals needed new bearings, Brake shoes wore out,
In six years of fooling around converting bikes, I have a couple of controllers with throttles just didn't make the cut for a bike, but they work as testers. A controller is 20-25 bucks. A throttle is 10 bucks, It might coast more for a Rad controller/display.
If you are dealing with fat tire motors, you need a 175mm stand. make it out of wood and two metal brackets. I have a spare 135m fat tire fork that I used for standard 135mm motors. The fat tire motors. I have to flip a bike upside down.
